// Copyright (C) 1999-2001 by Jason Hunter <jhunter_AT_acm_DOT_org>.
// All rights reserved. Use of this class is limited.
// Please see the LICENSE for more information.

package com.baomidou.framework.upload.multipart;

import java.io.IOException;

import javax.servlet.ServletInputStream;

/**
 * A <code>LimitedServletInputStream</code> wraps another
 * <code>ServletInputStream</code> in order to keep track of how many bytes have
 * been read and detect when the Content-Length limit has been reached. This is
 * necessary since some servlet containers are slow to notice the end of stream
 * and cause the client code to hang if it tries to read past it.
 * 
 * @author Jason Hunter
 * @author Geoff Soutter
 * @version 1.0, 2000/10/27, initial revision
 */
public class LimitedServletInputStream extends ServletInputStream {

	/** input stream we are filtering */
	private ServletInputStream in;

	/** number of bytes to read before giving up */
	private int totalExpected;

	/** number of bytes we have currently read */
	private int totalRead = 0;


	/**
	 * Creates a <code>LimitedServletInputStream</code> with the specified
	 * length limit that wraps the provided <code>ServletInputStream</code>.
	 */
	public LimitedServletInputStream( ServletInputStream in, int totalExpected ) {
		this.in = in;
		this.totalExpected = totalExpected;
	}


	/**
	 * Implement length limitation on top of the <code>readLine</code> method of
	 * the wrapped <code>ServletInputStream</code>.
	 *
	 * @param b
	 *            an array of bytes into which data is read.
	 * @param off
	 *            an integer specifying the character at which this method
	 *            begins reading.
	 * @param len
	 *            an integer specifying the maximum number of bytes to read.
	 * @return an integer specifying the actual number of bytes read, or -1 if
	 *         the end of the stream is reached.
	 * @exception IOException
	 *                if an I/O error occurs.
	 */
	public int readLine( byte b[], int off, int len ) throws IOException {
		int result, left = totalExpected - totalRead;
		if ( left <= 0 ) {
			return -1;
		} else {
			result = ((ServletInputStream) in).readLine(b, off, Math.min(left, len));
		}
		if ( result > 0 ) {
			totalRead += result;
		}
		return result;
	}


	/**
	 * Implement length limitation on top of the <code>read</code> method of the
	 * wrapped <code>ServletInputStream</code>.
	 *
	 * @return the next byte of data, or <code>-1</code> if the end of the
	 *         stream is reached.
	 * @exception IOException
	 *                if an I/O error occurs.
	 */
	public int read() throws IOException {
		if ( totalRead >= totalExpected ) {
			return -1;
		}

		int result = in.read();
		if ( result != -1 ) {
			totalRead++;
		}
		return result;
	}


	/**
	 * Implement length limitation on top of the <code>read</code> method of the
	 * wrapped <code>ServletInputStream</code>.
	 *
	 * @param b
	 *            destination buffer.
	 * @param off
	 *            offset at which to start storing bytes.
	 * @param len
	 *            maximum number of bytes to read.
	 * @return the number of bytes read, or <code>-1</code> if the end of the
	 *         stream has been reached.
	 * @exception IOException
	 *                if an I/O error occurs.
	 */
	public int read( byte b[], int off, int len ) throws IOException {
		int result, left = totalExpected - totalRead;
		if ( left <= 0 ) {
			return -1;
		} else {
			result = in.read(b, off, Math.min(left, len));
		}
		if ( result > 0 ) {
			totalRead += result;
		}
		return result;
	}
}
